In vitro activity: Methazolastone causes formation of DNA alkali-labile sites which are present in similar amounts and repaired at a similar rate in L-1210 and L-1210/BCNU cell lines. In L-1210 but not in L-1210/BCNU methazolastone induces an arrest of cells in SL-G2-M phases. Methazolastone sensitivity of both chemo-sensitive and resistant cells (D54-R and U87-R) is enhanced significantly under hyperoxia. Both Methazolastone and hyperoxia are associated with increased phosphorylation of ERK p44/42 MAPK (Erk1/2), but to a lesser extent in D54-R cells, suggesting that Erk1/2 activity may be involved in regulation of hyperoxia and Methazolastone-mediated cell death. Hyperoxia enhances Methazolastone toxicity in GBM cells by induction of apoptosis, possibly via MAPK-related pathways. Methazolastone induces in monocytes the DNA damage response pathways ATM-Chk2 and ATR-Chk1 resulting in p53 activation. Chronic Methazolastone exposure results in acquired Methazolastone-resistance and elevates miR-21 expression.

Cell Assay: L-1210 and L-1210/BCNU cells are seeded at 0.2 × 104 cells/mL and incubated for 24 hours. The cultures are treated with Methazolastone for l hours at 37oC, then washed twice in PBS by centrifugation and resuspended in fresh medium. Controls and treated samples are diluted in fresh medium 1:4 at 48 hours and 1:2 at 96 hours. Using these dilutions cell concentrations throughout the experiments are between 3 × 105 and 8 × 105/mL. Control growth is logarithmic in this range.